All of a sudden my car wont switch to gas and I get some warning beeps from the LPG system when I start the engine. I have a stag system fitted to an MG ZT 2.5 V6 petrol engine. When I connected it to my computer there is a warning/error that says the system needs to be checked by and LPG installer.

I thought that it could be the filter so I tried another one which I had lying around it seemed to work it switched to gas but I could smell gas so I checked the filter and gas was leaking from it so I put the original back on and again car does not switch to gas and the warning beeps are back when I start the engine.

I use a 12mm to 12mm Vapour Gas Filters and have ordered a replacement.

The question is if it is indeed the filter (I don't know for sure until the new one arrives) then I don't seem to having much luck with them as they don't seem to last a year I only do a small amount of miles around 2 to 3 k per annum. Is this normal or do I need a higher spec filter?

Brian you were right. When I went to replace the filter yesterday I suddenly realised that this message could be the service interval message so I removed it. I had already replaced the filter though so don't know for sure if this was what was stopping it from switching to gas or if the filter had just packed up at the same time I got the message.

Either way my car is switches to gas just fine now and runs smoothly. Thanks for the tip for checking the filter. Is it possible for the service interval message to stop it from switching to gas?

I can't see any other way for it to alert the driver its due a service besides either beeping or stopping it switching. I'd suspect only the later option would make a lot of people do anything about it. I've never bothered to enable it on mine.

I doubt theres much wrong with the filter - few people bother changing them, and only usually get changed when the system isn't working properly. Its not like the air filter or oil filter that clog up quickly, its more about catching debris from the tank/lines etc before they can get somewhere where they might cause damage. The main thing if you start messing round with them and decide to reuse it is make sure its the same way round it was to start with (ideally that will be the way it should be by the label, but if its reversed then don't put it back in the right way round, as anything caught will then be the wrong side of the filter!)